Edit: Metabase probably a fair alternative if they are likely to need the number of queries and views to increase, and even more so if you'd like to have them "self serve"
I definitely would not consider Superset unless you know that you need the advanced features.
Here's a CSV example https://bl.ocks.org/texodus/02d8fd10aef21b19d6165cf92e43e668 Here's a dashboard example (with a lot of data) https://texodus.github.io/nypd-ccrb/
The expectation is that data is loaded into your database, which is reasonable. None of these tools are built to ingest data from multiple disparate sources and perform their own aggregations (like Tableau), but rather depend on locality of data on the database under query.
[1] https://github.com/Markenson/csv-metabase-driver/releases/ta...
I'm also looking for suggestions. A client of ours has a classic CSV representing sales data. I want to build a dashboard to make the visualization of the dataset easier for the client. I was looking both for Metabase and Superset. However, I don't really know if there are any other products out there which could help in this. I'm obviously referring to open source products which could be easily deployed, so I'm removing tools like Tableau or PowerBI from the list.